The present invention relates to a three-line linear sensor, and specifically to a three-line linear sensor with an electronic shutter.
Because as R, G, B three-line color linear sensors are able to produce color information of higher resolution as compared with a two-line color linear sensor comprising a line with pixels of R, B dot-sequentially arrayed thereon or line of only G, they are frequently used in digital copiers and scanners. However, in the three-line color linear sensor, R, G, B sensor arrays (pixel arrays) are spaced apart spatially so that signals simultaneously output from the respective sensor arrays become information that is spaced apart spatially. Therefore, a position correction memory is provided in the outside of the three-line color linear sensor to correct the position information. This position correction memory needs a large memory capacity because the amount of positions to be corrected increases as a distance between sensor centers of sensor arrays (hereinafter referred to as "line spacing") increases. Accordingly, in order to reduce the required memory capacity and to make the system inexpensive, it is necessary to set a narrow line spacing.
There are known three-line color linear sensors having an electronic shutter provided at every line for controlling a storage time during which signal charges are accumulated in each photoelectric-conversion portion of sensor array.
FIG. 1 of the accompanying drawings shows such a three-line color linear sensor with the referenced electronic shutters.
As shown in FIG. 1, the three-line color linear sensor with electronic shutters includes lines having read-out gates 113, 123, 133 for reading out signal charges from photoelectric-converting sections 111, 121, 131 of sensor arrays 112, 122, 132 and CCD (charge-coupled device) analog shift registers 114, 124, 134 for transferring signal charges thus read out. In addition, electronic shutter structures 117, 127, 137 composing shutter gates 115, 125, 135 and shutter drains 116, 126, 136 are added to all lines.
Because the line spacings d are increased by the electronic shutter structures 117, 127, 137, the three-line color linear sensor with electronic shutter structures unavoidably requires a memory having a very large storage capacity as an external position correction memory, which makes the system very expensive. Accordingly, particularly in three-line color linear sensors with electronic shutter structures, in order to reduce the memory capacity and to make the system inexpensive, it is very important to reduce the line spacings d.